1. Field of the Invention
The present invention relates to a nozzle plate, an ink ejection head and an image forming apparatus, and more particularly, to a nozzle plate arranged in a recording head in an inkjet printer.
2. Description of the Related Art
In general, the inkjet printer uses alkaline ink, and the inkjet printer has an inkjet head constituted of a silicon substrate, which has a low resistance to alkali.
Japanese Patent Application Publication No. 2001-328263 discloses an inkjet head in which inner faces of a pressure chamber are formed in a silicon substrate and a face of a diaphragm facing the pressure chamber is also formed in the silicon substrate. Since the faces of the pressure chamber and the diaphragm make contact with the ink, then they are made resistant to alkali by being formed with a p-type doped layer on them.
However, in Japanese Patent Application Publication No. 2001-328263, the p-type doped layer is not formed on the nozzle plate. Then, edge portions that define ejection ports of nozzles in the nozzle plate do not have ink resistant properties, and it is not possible to maintain the dimensional accuracy of the ejection ports of the nozzles.
Moreover, in a case where a liquid repelling film is arranged on an ejection surface, which is the surface of the nozzle plate where the ejection ports of the nozzles are formed, the liquid repelling layer may be bonded on an oxide layer formed on the surface of the silicon substrate constituting the main body of the nozzle plate. In this case, since the bonding region between the oxide layer and the liquid repelling layer is exposed on the inner surface of the nozzle, then ink permeates through the bonding region, and there is a risk that the liquid repelling layer may peel away from the oxide layer formed on the silicon substrate.